check out the orfices before you go to replace them. many are adjustable for change over. if you take the orfice off look on the inside of the tube that you took it from and see if there is like a sharp pointed brass piece inserted in the tube that comes into contact with the orfice from the back side. tightening down the orfice reduces the flow of gas (cng) and loosening it increases gas flow (lpg). "CAUTION" LPG is heaver than air and if there are pilot
lights on the appliance it may necessitate lowering the physical location of the pilot light to accomidate this condition. This also leads to why boat owners are trying to get away from lpg "heaver than air means that it will settle in the low areas of the boat and become explosion hazards". Believe me, because my dad was blown up in the basement of an old house because of this very thing.